Translate README to Japanese

[tobySolutions]

Please translate the README.md file located at https://github.com/GaiaNet-AI/gaianet-node/blob/main/README.md into Japanese.

The translated file should be at: https://github.com/GaiaNet-AI/gaianet-node/blob/main/README-ja.md

Please ensure the translation is accurate and maintains the original meaning and intent of the document.

[oliverTwist2]

I want to work on this issue